A thermosensitive recording medium containing a thermosensitive recording layer, the major component of which are a colorless or pale colored electron donating leuco dye (henceforth referred to as “dye”) and an electron accepting color developing agent (henceforth referred to as “color developing agent”) that develops color when heated with the dye have found broad based practical applications. A thermal printer with an internally installed thermal head is ordinarily used to record on the thermosensitive recording medium. The thermosensitive recording mode is less noisy when recording, does not require a developing/fixing agent and is maintenance free, the device is relatively inexpensive and compact, and the color developed is very bright. Therefore, the thermosensitive recording mode is used in a broad range of applications such as facsimile devices, computer terminal printers, automatic ticket vending machines, meter recorders, handy terminals used outdoors and the like.
On the other hand, tacky labels having a tackifier layer on one side of paper are used extensively in labels such as price tag labels, merchandise labels, meter display labels, advertising labels and the like.
Furthermore, a thermosensitive recording label that combines a thermosensitive recording medium and a tacky label is ordinarily constructed by installing a tackifier layer containing a tackifier as a major component on the surface opposite to the thermosensitive recording layer. A thermosensitive recording label that uses a hot melt tackifier as the tackifier (Reference 1), a thermosensitive recording label that uses a heat activated tackifier containing a thermoplastic resin and a solid plasticizer as the tackifier (Reference 2), a thermosensitive recording label obtained by installing a intermediate layer between the substrate paper and the heat activated tackifier layer and using a hollow plastic pigment as a major component in the intermediate layer in order to improve the thermal efficiency of the heat activated tackifier during heating (Reference 3) and the like have been disclosed.
Such thermosensitive recording labels are used frequently under harsh conditions in applications such as frozen food labels, warning labels and logistics labels posted outside in extremely hot weather and the like in recent years, and the demand for water and weather resistance is increasing.
Therefore, the water and weather resistance of a thermosensitive recording label is ordinarily improved by installing a protective layer on the thermosensitive recording layer. (Reference 4 to 6)